Improvement in lockx



THOMAS STEWART. Improvement inA Locks.

Patented nec; 5, 1371.

No. :Z1-,680.

mpg/Ess sa,

PATENT FIE.

THOMAS STEWART, OF PHILADELPHIA, PENNSYLVANIA.

IMPROVEMENT IN LOCKS.

Specification forming part of Letters Patent No. 121,680, dated December5, 1871.

To all whom it may concern:

Be it known that I, THOMAS STEWART, of Philadelphia, in the county ofPhiladelphia and State of Pennsylvania, have invented an Improvement inLocks, of which the following is a specification My invention consistsof a key-hole guard, arranged within and combined with a door-lock, asfully described hereafter, so that when the door is locked from theinside the said guard shall slide with the bolt and cover the outerkey-hole, and so that when the door is locked or unlocked from theoutside the said guard shall merely rise and fall without sliding, and.serve as a supplementary tumbler for the bolt.

In the accompanying drawing, Figure l represents my improved lock,partly in section, with one of the side plates removed and the boltdrawn back; Fig. 2, the saine as Fig. 1, with the bolt shot forward;Figs. 3 and 4, the lock viewed from a side opposite that shown in Figs.l and 2; Fig. 5, a transverse section on the line l 2, Fig. l, showingthe operation of the key when inserted into the lock from the inner sideof the door; Fig. 6, a transverse section, showing the key inserted atthe opposite side; and Fig. 7, a sectional view of the lock on the line3 4, Fig. 2.

A represents the lock-case, of which a and a are the opposite sideplates; b, the front; c, the back; and d, the bottom; there being twokeyholes, e and e', in the side plates at points directly opposite eachother, the former of which is toward the outside and the latter towardthe inner side of the-door, to which the lock is attached. A bolt, B,is' arranged to slide in the lock-case, and is guided partly by theopeningf in the front of the latter, partly by projections g and h ofthe side plate a', and partly by a plate, D, secured within the lowerportion of the lockcase. A hole, e2, is formed in the plate D, on linewith the two key-holes, for the passage of a key, F, which can beinserted through either of the said key-holes for the purpose of forcingoutward or withdrawing the bolt after lifting a spring-tumbler', C, aprojection, i, on which is adapted to either of two notches, 7c 7c',formed on the upper edge of the said bolt. (See Figs. 1,2, and 7.) Theguard H, which forms the principal feature of my invention, is arrangedwithin the lock-case between the plate D and side plate a, and iscombined with the bolt in the manner which I will now proceed todescribe, so that when the door is locked from the inside the said guardshall be drawn forward by and with the bolt so as to cover the key-holee and thus prevent the introduction of a key through the latter from theoutside of the door; but so that when the door is locked from theoutside the said guard shall remain stationary, so as not to interferewith the introduction of a key from either side of the door. The saidguard has an arm, m, a pin, p, at the extremity of which enters a slot,p', formed in the bolt; and the guard is also provided with a lug, q,adapted to either of two notches, s and s', formed on the upper edgeofthe bolt, from either of which notches the said guard can be lifted,when drawn back, by means of a projection, t, on the key. (See Figs. 3and 6.)

The operation of the lock is as follows: When the parts are in theposition shown in Figs. 1, 3, and 5 and the key is introduced throughthe keyhole e and turned for the purpose of locking the door from theinside, the tumbler will be operated in the usual manner so as to firstpermit the bolt to slide forward, and then retain it; and the guard H,whose lug q is contained within the notch s of the bolt, and forms,therefore, in effect a part of the latter, will be carried forward withthe same, as shown in Figs. 2 and 1, so as to cover the outside key-holea. This, it will be evident, will effectually prevent the introductionof a key through the said outer key-hole c, or the picking of the' lockfrom the outside of the door by any of the instruments commonly used byburglars. The lifting of the guard so as to uncover the keyhole willalso be prevented by the projection h of the lock-case, which extendsover the lug q of the said guard. (See Fig. 2.) When the door isunlocked from the inside the sliding guard H will be drawn back with thebolt so as to again uncover the outer key-hole c. (See Fig. 3.) If it benow desired to lock the door from the outside the key is insertedthrough the outer keyhole c and turned, as shown in Fig. 6, when theguard, owing to the pressure of the projection t of the key against itsunder edge, will be lifted simultaneously with the tumbler, so as towithdraw its lug q from the notch s of the bolt, and thus permit thelatter to slide forward independently, (see dotted lines, Fig. 3,) theguard being prevented from following the bolt by the projection h of thelock-case, which is struck by the lug q of the said guard. When the dooris thus locked the lug q ofthe guard tnlls into the notrh s ofthe bolt,t'roni which it is lifted to ihll ueuin into the notch s of the szlidboltl when the hitter is drawn back.

It Will thus he seen that, while the guard loses the outer key-hole whenthe door is loeked t'ronl the inside, and thus prevents the pickin,"v ofthe i lock, it also serves :is u suppleinentury tumbler, 5

and increases the diliieulty ot' ithdruuing the bolt, except by theproper key, when the door is loeked from the outside.

I claim as my invention- The combination, With :i lock, of :1 keyhole

